That definitely looks like bumble foot. It's already spread and gotten large so I think it'll have to be surgically removed. If you have a vet that can remove and drain it, that's what you probably have to get to treat it. If you don't, you can do it yourself at home!
TREATING BUMBLEFOOT...
Be careful with the bathtub if there's no plastic cover to prevent slipping made specially for tubs. Something like - ( Bath Tub None Slip Mat ) With the salts, you should get the plain - none scented salts and that won't hurt her, unless you leave her in there too long with more salt than...
If she has bumble foot, use Epsom salts to soak her feet in, make sure she's not walking on hard ground, she had a very clean surface to walk on, ( maybe even keeping her inside or away from being in a muddy or dirty area ) her foot is wrapped, you have the medicine, and if it gets worse, you...